1. Field of the Invention
The present invention relates to a single-sided access device for DRAM applications. More particularly, the present invention relates to a single-sided multi-finger gate fin field-effect-transistor (FinFET) or single-gate FinFET with improved device control and access drive current, and a method for making the same.
2. Description of the Prior Art
As known in the art, dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Typically, DRAM is arranged in a square array of one capacitor and transistor per cell. The transistor, which acts as switching device, comprises a gate and a silicon channel region underneath the gate. The silicon channel region is located between a pair of source/drain regions in a semiconductor substrate and the gate is configured to electrically connect the source/drain regions to one another through the silicon channel region.
A vertical double-gate fin field-effect-transistor (FinFET) has been developed for the next-generation 4F2 DRAM cell (F stands for minimum lithographic feature width). However, difficulties are frequently encountered in attempting to produce the vast arrays of vertical double-gate FinFET devices desired for semiconductor DRAM applications while maintaining suitable performance characteristics of the devices. For example, recently DRAM manufacturers face a tremendous challenge on shrinking the memory cell area as the word line spacing, i.e., the spacing between two adjacent word lines, continues to shrink. For high-speed DRAM applications, electrical coupling effect may be a problem as the spacing between two closely arranged word lines continues to shrink. Further, it is desired to provide an improved FinFET access device with higher gate current and therefore better device performance.
In light of the above, there is a strong need in this industry to provide a novel FinFET structure and the fabrication process thereof in order to avoid the aforesaid problems.